1. Field of the Invention
The present invention generally relates to digital camera modules, and more particularly to a digital camera module with a small sized image sensor chip package which is used in portable electronic devices such as mobile phones, palm-top computers, personal digital assistants (PDAs) and so on.
2. Discussion of the Related Art
Generally, digital cameras are image recording media capable of photographing a plurality of still images without using film. Such a digital camera typically uses an image pickup device, which is a kind of semiconductor device, such as a charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS). In the digital camera, an object image formed on the image pickup device through a lens is converted into an electrical signal by the image pickup device, and the electrical signal is stored as a digital signal in a mobile phone or PDA in which the digital camera is mounted.
A typical digital camera module 100 is illustrated in FIG. 1. The digital camera module 100 is constructed to include a holder 11, a lens module 12 and an image sensor chip package 13. The lens module 12 includes a barrel 121, a lens 122, an IR (infra-red) cut filter 123 and a cover 124. The barrel 121 is placed in and threadingly engaged with the holder 11. The lens 122 is received in the barrel 121. The cover 124 is fixed to the barrel 121, on a front end of the barrel 121 which is exposed to outside. The cover 124 has a transparent area 125 which transmits light from outside to the lens 122. The IR-cut filter 123 is fixed to the barrel 121, opposite to the cover 124. The image sensor chip package 13 includes a bottom layer 131, a frame layer 132, an image sensor chip 133, a plurality of wires 134 and a transparent board 135. The bottom layer 131, which is made of printed circuit board (PCB), includes a plurality of top pads 1311 on a top surface thereof and a plurality of bottom pads 1312 on a bottom surface thereof. Each top pad 1311 corresponds and connects to a respective bottom pad 1312. The frame layer 132 is mounted on the top surface of the bottom layer 131, containing the top pads 1311 therein. The image sensor chip 133 is located on the top surface of the bottom layer 131, surrounded by the top pads 1311. The image sensor chip 133 includes a plurality of chip pads 1331 provided on a top surface thereof. Each chip pad 1331 is electrically connected with a corresponding top pad 1311 via a respective wire 134. The transparent board 135 is secured to the top of the frame layer 132. The image sensor chip package 13 is fixed to the holder 11, with the image sensor chip 133 facing the lens module 12.
In the digital camera module 100, the top surface of the bottom layer 131 peripherally surrounded by the frame layer 132 must contain the top pads 1311 and the image sensor chip 133 together, and sufficient space should be provided between the image sensor chip 133 and an inside wall of the frame 102 for movement of wire bonding tools used to connect the wires 134 with the chip pads 1331 and the top pads 1311. Therefore, package volume for packaging the chip 12 is a lot larger than that taken up by the chip 12, which results in a relative larger volume of the digital camera module 100. As such, the digital camera module 100 is not suitable for slim, compact electronic products.
What is needed, therefore, is a digital camera module with small size, high reliability and high image quality.